Power failure prevention circuit

Abstract

The invention relates to an anti-power-down circuit. The anti-power-down circuit comprises a first battery, a second battery, a discharging circuit and a booster circuit, wherein the first battery is connected with the discharging circuit; the rated voltage of the second battery is smaller than that of the first battery; the first battery is used for supplying power to the vehicle-mounted control system; the discharging circuit is used for conducting the second battery with the input end of the booster circuit under the condition that the output voltage of the first battery is smaller than a first preset voltage threshold value; and the booster circuit is used for boosting the input voltage of the input end of the booster circuit to the power supply voltage level required by the vehicle-mounted control system so as to supply power to the vehicle-mounted control system. The anti-power-down circuit provided by the invention can be used for continuously supplying power to the vehicle control system.

Description

Technical Field

[0001] This application relates to the technical field of electronic circuits, and particularly to a power-off prevention circuit. Background Art

[0002] With the development of automobiles, the power consumption of in-vehicle devices is increasing, resulting in an increasing burden on the in-vehicle battery. The in-vehicle battery may run out of power or fail under certain circumstances, causing the in-vehicle control system to lose power and the vehicle to malfunction.

[0003] Therefore, there is an urgent need for a circuit to prevent sudden power-off of automobiles. Summary of the Invention

[0004] Based on this, it is necessary to provide a power-off prevention circuit for preventing power-off of automobiles.

[0005] A power-off prevention circuit includes a first battery, a second battery, a discharge circuit, and a boost circuit, wherein:

[0006] The first battery is connected to the discharge circuit; the rated voltage of the second battery is less than the rated voltage of the first battery;

[0007] The first battery is used to supply power to the in-vehicle control system;

[0008] The discharge circuit is configured to conduct the second battery to the input end of the boost circuit when the output voltage of the first battery is less than a first preset voltage threshold;

[0009] The boost circuit is used to boost the input voltage at the input end of the boost circuit to the power supply voltage level required by the in-vehicle control system to supply power to the in-vehicle control system.

[0010] In one embodiment, the discharge circuit includes a switch unit, wherein:

[0011] The first end of the switch unit is connected to the second battery, the second end of the switch unit is connected to the boost circuit, and the control end of the switch unit is connected to the first battery;

[0012] The switch unit is configured to conduct the first end of the switch unit to the second end of the switch unit when the output voltage of the first battery received at the control end of the switch unit is less than the first preset voltage threshold.

[0013] In one embodiment, the switch unit includes a first MOS transistor and a first resistor, wherein:

[0014] The first end of the first resistor is grounded, the second end of the first resistor is connected to the control end of the first MOS transistor, the second end of the first resistor is also connected to the first battery, the first end of the first MOS transistor is connected to the second battery, and the second end of the first MOS transistor is connected to the boost circuit;

[0015] The first MOS transistor is configured to conduct the connection between the first end and the second end of the first MOS transistor when a ground signal is received at the control end of the first MOS transistor through the first resistor, or when the output voltage of the first battery is less than the first preset voltage threshold.

[0016] In one embodiment, the power-off prevention circuit further includes a microcontroller control circuit, where:

[0017] The microcontroller control circuit is configured to output a first voltage to the control end of the first MOS transistor when a low-level signal of the microcontroller is received; wherein, the first voltage is greater than or equal to the first preset voltage threshold;

[0018] The first MOS transistor is further configured to disconnect the connection between the first end and the second end of the first MOS transistor when the first voltage is received at the control end of the first MOS transistor.

[0019] In one embodiment, the microcontroller control circuit includes a first triode, a second triode, a second MOS transistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a seventh resistor, and the first voltage is the output voltage of the second battery, where:

[0020] The first end of the second resistor is connected to the single-chip microcomputer, the second end of the second resistor is connected to the first end of the third resistor, the second end of the third resistor is grounded, the first end of the third resistor is also connected to the control end of the first triode, the first end of the first triode is connected to the second end of the third resistor, the second end of the first triode is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded, the first end of the fourth resistor is also connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the second battery; the control end of the second triode is connected to the second end of the fifth resistor, the first end of the second triode is connected to the second battery, the second end of the second triode is connected to the first end of the seventh resistor, the second end of the seventh resistor is grounded, the first end of the seventh resistor is also connected to the control end of the second MOS transistor, the first end of the second MOS transistor is connected to the second battery, and the second end of the second MOS transistor is connected to the control end of the first MOS transistor;

[0021] When the vehicle-mounted control system needs to be powered, the single-chip microcomputer inputs a high-level signal to the first end of the second resistor, the first end and the second end of the first triode are turned on, the control end of the second triode receives a voltage signal less than the second preset voltage threshold, the first end and the second end of the second triode are turned on, the control end of the second MOS transistor receives a voltage signal greater than or equal to the third preset voltage threshold, and the first end and the second end of the second MOS transistor are not turned on;

[0022] When the vehicle-mounted control system does not need to be powered, the single-chip microcomputer inputs a low-level signal to the first end of the second resistor, the first end and the second end of the first triode are not turned on, the control end of the second triode receives a voltage signal greater than the second preset voltage threshold, the first end and the second end of the second triode are not turned on, the control end of the second MOS transistor is grounded through the seventh resistor, the first end and the second end of the second MOS transistor are turned on, the output voltage of the second battery is transmitted to the control end of the first MOS transistor, and the first end and the second end of the first MOS transistor are not turned on.

[0023] In one embodiment, the power-off prevention circuit further includes a charging circuit, where:

[0024] The charging circuit is connected to a standard voltage source, and is also connected to the second battery and the first battery; the standard voltage source is obtained by step-down processing of the first battery;

[0025] The charging circuit is configured to step down the standard voltage source and charge the second battery when the voltage of the first battery is greater than or equal to a fourth preset voltage threshold.

[0026] In one embodiment, the charging circuit includes a charging management chip and a charging enable circuit, where:

[0027] A first end of the charging enable circuit is connected to the first battery, and a second end of the charging enable circuit is connected to an enable signal terminal of the charging management chip; the charging management chip is also connected to the standard voltage source;

[0028] The charging enable circuit is configured to output a charging enable signal to the enable signal terminal of the charging management chip when the voltage of the first battery received at the first end of the charging enable circuit is greater than or equal to the fourth preset voltage threshold; and is further configured to output a grounding signal to the enable signal terminal of the charging management chip when the voltage of the first battery received at the first end of the charging enable circuit is less than the fourth preset voltage threshold;

[0029] The charging management chip is configured to step down the voltage provided by the standard voltage source and output the stepped-down voltage to the second battery to charge the second battery when the enable signal terminal of the charging management chip receives the charging enable signal.

[0030] In one embodiment, the charging enable circuit includes an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third MOS transistor, and a fourth MOS transistor, and the charging enable signal is an output voltage signal of the standard voltage source, where:

[0031] The first end of the eighth resistor is connected to the first battery, the second end of the eighth resistor is connected to the first end of the ninth resistor, and the second end of the ninth resistor is grounded; the control end of the third MOS transistor is connected to the second end of the eighth resistor, the first end of the third MOS transistor is grounded, the second end of the third MOS transistor is connected to the first end of the tenth resistor, and the second end of the tenth resistor is connected to the standard voltage source; the control end of the fourth MOS transistor is connected to the first end of the tenth resistor, the first end of the fourth MOS transistor is grounded, the second end of the fourth MOS transistor is connected to the first end of the eleventh resistor, the second end of the eleventh resistor is connected to the standard voltage source, and the first end of the eleventh resistor is further connected to the enable signal terminal of the charging management chip;

[0032] When the output voltage of the first battery is greater than or equal to the fourth preset voltage threshold, the first end and the second end of the third MOS transistor are turned on, the control end of the fourth MOS transistor is grounded through the third MOS transistor, the first end and the second end of the fourth MOS transistor are not turned on, and the standard voltage source outputs the output voltage signal to the enable signal terminal of the charging management chip through the eleventh resistor;

[0033] When the output voltage of the first battery is less than the fourth preset voltage threshold, the first end and the second end of the third MOS transistor are not turned on, the standard voltage source outputs a voltage to the control end of the fourth MOS transistor through the tenth resistor, the first end and the second end of the fourth MOS are turned on, and the enable signal terminal of the charging management chip is grounded through the fourth MOS transistor.

[0034] In one embodiment, the charging circuit further includes a fuse, where:

[0035] The first end of the fuse is connected to the charging management chip, and the second end of the fuse is connected to the second battery;

[0036] The charging management chip is further configured to step down the voltage provided by the standard voltage source and output it to the second battery through the fuse to charge the second battery when the enable signal terminal of the charging management chip receives the charging enable signal.

[0037] In one embodiment, the charging circuit further includes a first indicator light and a second indicator light, where:

[0038] The first indicator light is connected to the charging management chip, and the second indicator light is connected to the charging management chip;

[0039] The charging management chip is further configured to light the first indicator light during the charging process of the second battery;

[0040] The charging management chip is further configured to light the second indicator light when the charging of the second battery is completed.

[0041] In the above anti-power-off circuit, through the dual-battery redundancy design, when the main battery (the first battery) fails (such as power shortage, short circuit, open circuit), the backup battery is automatically connected and provides a stable voltage through the boost circuit, avoiding the failure of in-vehicle control systems (such as ECU, instrument panel) due to power-off, ensuring the continuous operation of key vehicle functions (such as brake assist, communication system), and improving driving safety. In addition, the above anti-power-off circuit realizes seamless switching and stable output of power through a three-layer architecture of "main and backup batteries + threshold detection + boost conversion", uses a low-voltage backup battery in cooperation with the boost circuit to reduce system costs, and at the same time ensures power supply reliability through threshold control, solving the power-off risk of in-vehicle devices caused by power problems at the hardware level. Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0043] Figure 1 It is a schematic structural diagram of an anti-power-off circuit in an embodiment;

[0044] Figure 2 It is a schematic structural diagram of a discharge circuit and a single-chip microcomputer control circuit in an embodiment;

[0045] Figure 3 It is a schematic structural diagram of a boost circuit in an embodiment;

[0046] Figure 4 It is a schematic structural diagram of an anti-power-off circuit in another embodiment;

[0047] Figure 5 It is a schematic structural diagram of an anti-power-off circuit in yet another embodiment;

[0048] Figure 6 It is a schematic structural diagram of a charging circuit in an embodiment. Detailed Embodiments

[0049] For ease of understanding of this application, the following will provide a more comprehensive description of this application with reference to the relevant accompanying drawings. Embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0051] It can be understood that the terms "first", "second", etc. used in this application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor can be referred to as a second resistor, and similarly, a second resistor can be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0052] It can be understood that for "connection" in the following embodiments, if there is an electrical signal or data transfer between the connected circuits, modules, units, etc., it should be understood as "electrical connection", "communication connection", etc.

[0053] It can be understood that "at least one" means one or more, and "a plurality" means two or more. "At least a part of an element" means part or all of the element.

[0054] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprise / include" or "have" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the related listed items.

[0055] In an exemplary embodiment, as Figure 1 shown, the power-fail protection circuit includes a first battery 10, a second battery 20, a discharge circuit 30, and a boost circuit 40, where:

[0056] The above-mentioned first battery 10 is connected to the above-mentioned discharge circuit 30; the rated voltage of the above-mentioned second battery 20 is less than the rated voltage of the above-mentioned first battery 10; the above-mentioned first battery 10 is used to supply power to the vehicle-mounted control system; the above-mentioned discharge circuit 30 is used to conduct the above-mentioned second battery 20 to the input end of the above-mentioned boost circuit 40 when the output voltage of the above-mentioned first battery 10 is less than the first preset voltage threshold; the above-mentioned boost circuit 40 is used to boost the input voltage at the input end of the above-mentioned boost circuit 40 to the power supply voltage level required by the above-mentioned vehicle-mounted control system to supply power to the above-mentioned vehicle-mounted control system.

[0057] Among them, the power-off prevention circuit can refer to an electronic circuit used to prevent the vehicle-mounted control system from losing power due to a sudden drop or failure of the power supply voltage. Through a dual-battery configuration and an automatic switching mechanism, it ensures that when the main battery voltage is insufficient, the backup battery can take over the power supply to maintain the stable operation of the vehicle-mounted control system.

[0058] Among them, the first battery 10 can be the main battery with a relatively high rated voltage (such as a vehicle-mounted battery with a voltage of 12V or 24V, etc.). The first battery 10 directly provides the conventional working voltage for the vehicle-mounted control system and serves as the main power source of the system. In this embodiment, the first battery 10 of the power-off prevention circuit can be directly connected to the vehicle-mounted battery without the need to additionally connect a battery.

[0059] Among them, the second battery 20 can be the backup battery with a rated voltage lower than that of the first battery 10 (such as a lithium battery with a voltage of 3.7V or 4.1V, etc.).

[0060] Among them, the discharge circuit 30 can be a signal detection and switching control module that monitors the output voltage of the first battery 10 in real time. When the output voltage of the first battery 10 is lower than the first preset voltage threshold, it conducts the connection between the second battery 20 and the boost circuit 40 to trigger the access of the backup power supply.

[0061] Among them, the boost circuit 40 can refer to a voltage conversion module that boosts the low-voltage input of the second battery 20 to the rated voltage level required by the vehicle-mounted control system to ensure that the backup power supply can meet the power supply requirements of the vehicle-mounted control system.

[0062] Among them, the first preset voltage threshold can be used to determine whether the first battery 10 has a too low output voltage due to insufficient power or failure and cannot effectively supply power to the vehicle-mounted system, serving as the trigger condition for switching to the backup power supply; the first preset voltage threshold can be set according to actual needs and is not specifically limited here.

[0063] Specifically, the principle of the above anti-power-off circuit is described as follows: The first preset voltage threshold can be the conventional voltage required for the power supply of the vehicle control system. The discharge circuit 30 monitors the voltage of the first battery 10. When the voltage of the first battery 10 is greater than or equal to the conventional voltage required for the power supply of the vehicle control system, it is the normal power supply mode. The first battery 10 directly supplies power to the vehicle control system, and the discharge circuit 30 does not operate, that is, the second battery 20 is not connected to the input end of the boost circuit 40. When the voltage of the first battery 10 is less than the conventional voltage required for the power supply of the vehicle control system, it is the standby power supply trigger condition. The discharge circuit 30 detects that the voltage of the first battery 10 is abnormal and conducts the output end of the second battery 20 to the input end of the boost circuit 40. The second battery 20 is connected to the boost circuit 40 through the discharge circuit 30. The boost circuit 40 converts the low voltage transmitted by the second battery 20 into the conventional voltage required by the vehicle control system to supply power to the control system instead of the first battery 10, avoiding the power-off failure caused by the failure of the main power supply. The second battery 20 is only enabled when the voltage of the first battery 10 is insufficient and is in a standby state under normal conditions, ensuring that the main power supply supplies power first. At the same time, the second battery 20 can be charged through the charging circuit to maintain the power reserve of the second battery 20.

[0064] In some other embodiments, if the first battery 10 is detected and the battery voltage has been lower than the first preset voltage threshold, but remains at a voltage slightly lower than the first preset voltage threshold and the output is relatively stable, it can be considered to connect the first battery 10 to the boost circuit 40 through the discharge circuit 30, and then boost the voltage through the boost circuit 40 to supply power to the vehicle control system for a short time.

[0065] In the above anti-power-off circuit, through the dual-battery redundancy design, when the main battery (the first battery 10) fails (such as power shortage, short circuit, open circuit), the standby battery is automatically connected and provides a stable voltage through the boost circuit 40, avoiding the failure of the vehicle control system (such as ECU, dashboard) due to power-off, and ensuring the continuous operation of key vehicle functions (such as brake assist, communication system), improving driving safety. In addition, the above anti-power-off circuit realizes seamless switching and stable output of the power supply through a three-layer architecture of "main and standby batteries + threshold detection + boost conversion", uses a low-voltage standby battery in cooperation with the boost circuit 40 to reduce the system cost, and at the same time ensures the power supply reliability through threshold control, solving the power-off risk of in-vehicle devices caused by power supply problems at the hardware level.

[0066] In an exemplary embodiment, the above-mentioned discharge circuit 30 includes a switch unit, where: the first end of the switch unit is connected to the second battery 20, the second end of the switch unit is connected to the boost circuit 40, and the control end of the switch unit is connected to the first battery 10; the switch unit is configured to conduct the connection between the first end and the second end of the switch unit when the output voltage of the first battery 10 received at the control end of the switch unit is less than the first preset voltage threshold.

[0067] Among them, the switch unit can refer to the core component in the discharge circuit 30, which can be an electronic switch with a control function and can determine the on or off state between its first end and second end according to the signal at the control end. Commonly used electronic switches include, for example, MOSFET (MOS transistor), triode, etc.; the control of the switch state can be achieved by controlling the voltage of its gate (for MOSFET) or base (for triode).

[0068] Specifically, the normal power supply state is: when the output voltage of the first battery 10 is greater than or equal to the first preset voltage threshold, the voltage signal received at the control end of the first switch unit indicates that the first battery 10 is working properly. At this time, the first switch unit is in the off state, that is, there is no conduction between the first end and the second end of the first switch unit, and there is no current path between the second battery 20 and the boost circuit 40, and the vehicle-mounted control system is directly powered by the first battery 10. The trigger for the standby power supply state is: when the output voltage of the first battery 10 drops to less than the first preset voltage threshold, this means that the first battery 10 may have insufficient power or a fault and cannot provide enough voltage for the vehicle-mounted control system. At this time, the voltage signal received at the control end of the first switch unit triggers the switch action, and the first switch unit conducts its first end and second end. In this way, a current path is formed between the second battery 20 and the boost circuit 40, and the electrical energy of the second battery 20 can be transmitted to the boost circuit 40 through the first switch unit.

[0069] In this embodiment, through the switch unit, when the output voltage of the first battery 10 is insufficient, the second battery 20 is automatically connected to the circuit without manual intervention, which improves the reliability and response speed of the anti-power-off circuit. When the first battery 10 has a problem, it can quickly switch to the second battery 20 for power supply to ensure the continuous operation of the vehicle-mounted control system. In addition, using the first switch unit as the core control component, the circuit structure is relatively simple, which can reduce costs.

[0070] In an exemplary embodiment, as Figure 2As shown, the above switch unit includes a first MOS transistor Q19 and a first resistor R610, where: the first end of the first resistor R610 is grounded, the second end of the first resistor R610 is connected to the control end of the first MOS transistor Q19, the second end of the first resistor R610 is also connected to the first battery 10, the first end of the first MOS transistor Q19 is connected to the second battery 20, and the second end of the first MOS transistor Q19 is connected to the boost circuit 40; the first MOS transistor Q19 is configured to conduct the first end and the second end of the first MOS transistor Q19 when the control end of the first MOS transistor Q19 receives a ground signal through the first resistor R610, or when the output voltage of the first battery 10 received is less than the first preset voltage threshold.

[0071] Among them, the MOS transistor may refer to a metal-oxide-semiconductor field-effect transistor; in this embodiment, as Figure 2As shown, when the first battery 10 (VBP) fails, the control terminal of the first MOS transistor Q19 is grounded through the first resistor R610 (pull-down resistor) and receives a ground signal, causing the first MOS transistor Q19 to conduct. The first terminal of the first MOS transistor Q19 (the port connected to the VBAT point) is connected to the second terminal of the first MOS transistor Q19 (the port connected to the VBAT_R point), that is, the second battery 20 (VBAT) is connected to the input terminal (VBAT_R) of the boost circuit 40. The second battery 20 is connected to the boost circuit 40 through the conducting MOS transistor to maintain system power supply. When the first battery 10 (VBP) has an output voltage, and the output voltage obtained by dividing the voltage through the first resistor R610 and the current-limiting resistor R611 at the control terminal of the first MOS transistor Q19 is greater than or equal to the first preset voltage threshold, the first MOS transistor Q19 is turned off, and the second battery 20 (VBAT) is disconnected from the input terminal (VBAT_R) of the boost circuit 40, and the system is powered by the first battery 10. When the output voltage obtained by dividing the voltage through the first resistor R610 and the current-limiting resistor R611 at the control terminal of the first MOS transistor Q19 is less than the first preset voltage threshold, that is, when the output voltage of the first battery 10 (VBP) drops and the voltage at the voltage-dividing point is lower than the first preset voltage threshold, the first MOS transistor Q19 conducts, and the second battery 20 is connected to the boost circuit 40 through the conducting MOS transistor to maintain system power supply. Specifically, when the first preset voltage threshold is the output voltage of the second battery 20, when the first battery 10 is operating normally, the output voltage of the first battery 10 reaches the control terminal of the first MOS transistor Q19 through the resistor R611 and the switching diode D447. At this time, the voltage at the control terminal of the first MOS transistor Q19 is higher than the voltage at the first terminal of the first MOS transistor Q19 (the output voltage of the second battery 20), so the first MOS transistor Q19 does not conduct, and thus the discharge circuit 30 does not operate, and the boost circuit 40 does not operate either.

[0072] In an exemplary embodiment, the boost circuit 40 may be as Figure 3 shown, and the boost circuit 40 includes Figure 3The connections are as follows: DC-DC chip U2, DC-DC shutdown DCDC control resistor R20, Schottky diodes D87 and D88, voltage divider feedback DC-DC resistors R21, R23, and R28, filter capacitors C258, C260, C261, C262, and C265, and freewheeling inductor L1. Pin 1 (SW) of DC-DC chip U2 is the drain of the internal switch, pin 2 (GND) is the power ground, pin 3 (FB) is used to connect to the external voltage divider feedback point, and pin 4 (SHDN) is the shutdown control input. If this function is not used, connect this pin to the Vin network, that is, connect it to the input terminal (VBAT_R) that transmits the output voltage of the second battery 20 through the DC-DC shutdown DCDC control resistor R20. Conversely, connecting pin 4 (SHDN) to ground shuts down the DC-DC chip, thus disabling the boost function. Pin 5 (VUB) is the power input. Here, VDD_R represents the 5V boosted by the boost circuit 40, and P5V represents the 5V used by other circuits. Schottky diodes D87 and D88 prevent 5V backflow within the circuit. When the input terminal (VBAT_R) of the boost circuit 40 is connected to the second battery 20 (VBAT), that is, when receiving the output voltage of the second battery 20, the boost circuit 40 boosts the output voltage of the second battery 20 to produce a 5V voltage (the rated voltage level required by the vehicle control system in this embodiment is 5V).

[0073] In an exemplary embodiment, Figure 4 As shown, the power-off prevention circuit further includes a single-chip microcomputer control circuit 50, wherein: the single-chip microcomputer control circuit 50 is configured to output a first voltage to the control terminal of the first MOS transistor Q19 when receiving a low-level signal from the single-chip microcomputer; wherein the first voltage is greater than or equal to the first preset voltage threshold; and the first MOS transistor Q19 is further configured to disconnect the first terminal of the first MOS transistor Q19 from the second terminal of the first MOS transistor Q19 when the control terminal of the first MOS transistor Q19 receives the first voltage.

[0074] Among them, the single-chip microcomputer control circuit 50 can refer to a circuit that outputs after receiving the control signal (such as a low-level signal or a high-level signal) of the single-chip microcomputer. For example, when the second battery 20 powers the vehicle control system through the discharge circuit 30 and the boost circuit 40, if it is desired to stop the second battery 20 from discharging to the vehicle control system, the single-chip microcomputer can output a low-level signal to the above-mentioned single-chip microcomputer control circuit 5050, and the single-chip microcomputer control circuit 5050 outputs a first voltage greater than or equal to the first preset voltage threshold to the control terminal of the first MOS transistor Q19. When the first MOS transistor Q19 receives a voltage greater than or equal to the first preset voltage threshold, the first end of the first MOS transistor Q19 is disconnected from the second end of the first MOS transistor Q19, achieving an open state, cutting off the connection between the second battery 20 and the boost circuit 40, and stopping power supply to the vehicle control system.

[0075] In another embodiment, when the control signal output by the single-chip microcomputer is a high-level signal, the single-chip microcomputer control circuit 50 outputs a voltage less than the first preset voltage threshold to the control terminal of the first MOS transistor Q19. When the first MOS transistor Q19 receives a voltage less than the first preset voltage threshold, the first end of the first MOS transistor Q19 is conducted with the second end of the first MOS transistor Q19, achieving a closed state, conducting the connection between the second battery 20 and the boost circuit 40, and supporting power supply to the vehicle control system. Therefore, except for the case where it is desired to stop power supply to the vehicle control system, the control signal output by the single-chip microcomputer in the above anti-power-off circuit is generally a high-level signal to support when the first battery 10 has a power shortage or is suddenly damaged due to a collision, resulting in the output voltage of the first battery 10 being less than the first preset voltage threshold, the first MOS transistor Q19 can achieve a conducting state, and then conduct the second battery 20 and the boost circuit 40 to realize power supply from the second battery 20 to the vehicle control system.

[0076] In an exemplary embodiment, as Figure 2 shown, the single-chip microcomputer control circuit 50 includes a first triode Q18, a second triode Q20, a second MOS transistor Q16, a second resistor R621, a third resistor R620, a fourth resistor R617, a fifth resistor R618, a sixth resistor R619, a seventh resistor R616, and the above first voltage is the output voltage of the second battery 20, where:

[0077] The first end of the second resistor R621 is connected to the single-chip microcomputer (VBAT_EN point), the second end of the second resistor R621 is connected to the first end of the third resistor R620, the second end of the third resistor R620 is grounded, the first end of the third resistor R620 is also connected to the control end of the first triode Q18, the first end of the first triode is connected to the second end of the third resistor R620, the second end of the first triode Q18 is connected to the first end of the fourth resistor R617, the second end of the fourth resistor R617 is grounded, the first end of the fourth resistor R617 is also connected to the first end of the fifth resistor R618, the second end of the fifth resistor R618 is connected to the first end of the sixth resistor R619, the second end of the sixth resistor R619 is connected to the second battery 20 (VABT point); the control end of the second triode Q20 is connected to the second end of the fifth resistor R618, the first end of the second triode Q20 is connected to the second battery 20 (VABT point), the second end of the second triode Q20 is connected to the first end of the seventh resistor R616, the second end of the seventh resistor R616 is grounded, the first end of the seventh resistor R616 is also connected to the control end of the second MOS transistor Q16, the first end of the second MOS transistor Q16 is connected to the second battery 20, and the second end of the second MOS transistor Q16 is connected to the control end of the first MOS transistor Q19.

[0078] When power supply is required for the in-vehicle control system, the single-chip microcomputer inputs a high-level signal to the first end of the second resistor R621. The first end and the second end of the first triode Q18 are turned on. The control end of the second triode Q20 receives a voltage signal less than the second preset voltage threshold. The first end and the second end of the second triode Q20 are turned on. The control end of the second MOS transistor Q16 receives a voltage signal greater than or equal to the third preset voltage threshold. The first end and the second end of the second MOS transistor Q16 are not turned on.

[0079] Specifically, when the first battery 10 is normal, the single-chip microcomputer inputs a high-level signal to the first end of the second resistor R621. The second resistor R621 and the third resistor R620 divide the voltage to turn on the first triode Q18. At this time, the output voltage of the second battery 20 divides the voltage through the fifth resistor R618 and the sixth resistor R619 to turn on the second triode Q20. At this time, the voltage at the control end of the second MOS transistor Q16 (the output voltage of the second battery 20) is equal to the voltage at the first end of the second MOS transistor Q16 (the output voltage of the second battery 20. At this time, the third preset voltage threshold is the output voltage value of the second battery 20), so the second MOS transistor Q16 is not turned on. Another example isFigure 2 As shown, at this time, the first battery 10 is normal, and the voltage of the first battery 10 is divided by the resistor R611 and the first resistor R610 and supplied to the control terminal of the first MOS transistor Q19. At this time, the voltage at the control terminal of the first MOS transistor Q19 is higher than the voltage at the first terminal of the first MOS transistor Q19 (the output voltage of the second battery 20). Therefore, the first MOS transistor Q19 is not turned on, so the discharge circuit 30 does not work, and the boost circuit 40 will not work either.

[0080] When the vehicle-mounted control system does not need to be powered, the single-chip microcomputer inputs a low-level signal to the first terminal of the second resistor R621. The first terminal of the first triode Q18 and the second terminal of the second triode Q20 are not turned on. The control terminal of the second triode Q20 receives a voltage signal greater than the second preset voltage threshold. The first terminal and the second terminal of the second triode Q20 are not turned on. The control terminal of the second MOS transistor Q16 is grounded through the seventh resistor R616. The first terminal and the second terminal of the second MOS transistor Q16 are turned on, and the output voltage of the second battery 20 is transmitted to the control terminal of the first MOS transistor Q19. The first terminal and the second terminal of the first MOS transistor Q19 are not turned on.

[0081] Specifically, refer to Figure 2When the first battery 10 suddenly loses power or is suddenly damaged due to a collision, resulting in a power failure, since the single-chip microcomputer inputs a high-level signal to the first end of the second resistor R621, the single-chip microcomputer control circuit 50 still does not output voltage to the control end of the first MOS transistor Q19. At this time, due to the power failure of the first battery 10 connected to the control end of the first MOS transistor Q19 and the effect of the first resistor R610 pulling down to the ground, the voltage obtained by voltage division at the control end of the first MOS transistor Q19 is less than the voltage at the first end of the first MOS transistor Q19 (the output voltage of the second battery 20). At this time, the first MOS transistor Q19 conducts, and then the second battery 20 is connected to the boost circuit 40, and the second battery 20 supplies power to the vehicle-mounted control system. At this time, if the vehicle-mounted control system wants to sleep and cut off power after completing its work, a low-level signal can be input to the first end of the second resistor R621 through the single-chip microcomputer. At this time, the first triode Q18 does not conduct, and the fourth resistor R617, the fifth resistor R618, and the sixth resistor R619 perform voltage division, and the second triode Q20 does not conduct. The control end of the second MOS transistor Q16 is grounded through the seventh resistor R616, and the voltage at its control end is lower than the voltage at the first end of the second MOS transistor Q16 (the output voltage of the second battery 20). At this time, the second MOS transistor Q16 conducts, and the output voltage of the second battery 20 is transmitted to the control end of the first MOS transistor Q19 through the resistor R612 and the switching diode D449. At this time, since the voltage at the control end of the first MOS transistor Q19 is the output voltage of the second battery 20, which is equal to the voltage at the first end of the control end of the first MOS transistor Q19, both being the output voltage of the second battery 20, the first MOS transistor Q19 does not conduct. At this time, the second battery 20 is disconnected from the boost circuit 40, that is, it no longer supplies power to the vehicle-mounted control system, realizing sleep and power-off.

[0082] In the Figure 2 discharge circuit 30 and the single-chip microcomputer control circuit 50 shown, R617, R618, R619, R620, and R621 are voltage-dividing resistors. The first triode Q18 can be an NPN triode for controlling the ground. The second triode Q20 can be a PNP triode. The second MOS transistor Q16 can be a Pmos transistor. The first MOS transistor Q19 can be a Pmos transistor. D446 can be a zener diode.

[0083] In an exemplary embodiment, as Figure 5As shown, the above anti-power-off circuit further includes a charging circuit 60, where: the charging circuit is connected to a standard voltage source, the charging circuit is further connected to the second battery 20, and the charging circuit is further connected to the first battery 10; the standard voltage source is obtained by step-down processing of the first battery 10; the charging circuit is configured to, when the voltage of the first battery 10 is greater than or equal to a fourth preset voltage threshold, step down the standard voltage source and then charge the second battery 20.

[0084] Specifically, the fourth preset voltage threshold may be a set voltage value for determining whether the output voltage of the first battery 10 is normal; the charging circuit is used to manage the charging process of the second battery 20 to ensure that it is charged when the voltage of the first battery 10 is normal and stops charging when the voltage is insufficient to give priority to ensuring system power supply. The standard voltage source may be a stable voltage obtained by step-down processing of the first battery 10 and used as the input of the charging circuit. For example, if the first battery 10 is 12V, the standard voltage source may be 5V, depending on the actual charging requirements of the second battery 20. In a vehicle control system, the standard voltage source may refer to the common 5V voltage obtained by step-down processing of the first battery 10 in an off-the-shelf circuit. Therefore, the anti-power-off circuit in this application can directly obtain the common 5V voltage in the vehicle control system, and the second battery 20 (lithium battery) can be used in cooperation with the charging circuit and arranged inside the controller of the vehicle control system.

[0085] In an exemplary embodiment, as Figure 6 shown, the charging circuit includes a charging management chip U5 and a charging enable circuit, where: the first end of the charging enable circuit is connected to the first battery 10, and the second end of the charging enable circuit is connected to the enable signal terminal of the charging management chip U5; the charging management chip U5 is further connected to the standard voltage source; the charging enable circuit is configured to, when the voltage of the first battery 10 received at the first end of the charging enable circuit is greater than or equal to the fourth preset voltage threshold, output a charging enable signal to the enable signal terminal of the charging management chip U5; and is further configured to, when the voltage of the first battery 10 received at the first end of the charging enable circuit is less than the fourth preset voltage threshold, output a grounding signal to the enable signal terminal of the charging management chip U5; the charging management chip U5 is configured to, when the charging enable signal is received at the enable signal terminal of the charging management chip U5, step down the voltage provided by the standard voltage source and output it to the second battery 20 to charge the second battery 20.

[0086] Among them, the charging management chip U5 is used to intelligently control the charging process of the second battery 20. The charging enable circuit generates a charging enable signal or a ground signal based on the first battery 10 to control the working state of the charging management chip U5. The enable signal terminal of the charging management chip U5 may refer to the control pin of the charging management chip U5. A high level (charging enable signal) activates the charging function, and a low level (ground signal) disables the charging. The fourth preset voltage threshold may be a set voltage value used to determine whether the output voltage of the first battery 10 is normal. The specific set voltage value can be determined according to actual requirements. When the output voltage of the first battery 10 is abnormal, that is, when its voltage is less than the fourth preset voltage threshold, the charging process of the second battery 20 is stopped because at this time the first battery 10 cannot normally supply power to the vehicle control system and the second battery 20 needs to supply power. The charging process of the second battery 20 is stopped so that the second battery 20 can start the discharging process.

[0087] In an exemplary embodiment, as Figure 6 shown, the above-mentioned charging enable circuit includes an eighth resistor R62, a ninth resistor R63, a tenth resistor R57, an eleventh resistor R608, a third MOS transistor Q7, and a fourth MOS transistor Q6. The above-mentioned charging enable signal is the output voltage signal of the above-mentioned standard voltage source, where:

[0088] The first end of the above-mentioned eighth resistor R62 is connected to the above-mentioned first battery 10, the second end of the above-mentioned eighth resistor R62 is connected to the first end of the above-mentioned ninth resistor R63, and the second end of the above-mentioned ninth resistor R63 is grounded; the control end of the above-mentioned third MOS transistor Q7 is connected to the second end of the above-mentioned eighth resistor R62, the first end of the above-mentioned third MOS transistor Q7 is grounded, the second end of the above-mentioned third MOS transistor Q7 is connected to the first end of the above-mentioned tenth resistor R57, and the second end of the above-mentioned tenth resistor R57 is connected to the above-mentioned standard voltage source; the control end of the above-mentioned fourth MOS transistor Q6 is connected to the first end of the above-mentioned tenth resistor R57, the first end of the above-mentioned fourth MOS transistor Q6 is grounded, the second end of the above-mentioned fourth MOS transistor Q6 is connected to the first end of the above-mentioned eleventh resistor R608, the second end of the above-mentioned eleventh resistor R608 is connected to the above-mentioned standard voltage source, and the first end of the above-mentioned eleventh resistor R608 is also connected to the enable signal terminal of the above-mentioned charging management chip U5.

[0089] When the output voltage of the above-mentioned first battery 10 is greater than or equal to the fourth preset voltage threshold, the first end and the second end of the above-mentioned third MOS transistor Q7 are conducted, the control end of the above-mentioned fourth MOS transistor Q6 is grounded through the above-mentioned third MOS transistor Q7, the first end and the second end of the above-mentioned fourth MOS transistor Q6 are not conducted, and the above-mentioned standard voltage source outputs the above-mentioned output voltage signal to the enable signal terminal of the above-mentioned charging management chip U5 through the above-mentioned eleventh resistor R608.

[0090] When the output voltage of the first battery 10 is less than the fourth preset voltage threshold, the first end and the second end of the third MOS transistor Q7 are not conducting. The standard voltage source outputs a voltage to the control end of the fourth MOS transistor Q6 through the tenth resistor R57. The first end and the second end of the fourth MOS transistor Q6 are conducting, and the enable signal terminal of the charging management chip U5 is grounded through the fourth MOS transistor Q6.

[0091] Specifically, as Figure 6 shown, when the output voltage of the first battery 10 (VBP) is normal, that is, when the output voltage of the first battery 10 is greater than or equal to the fourth preset voltage threshold, the output voltage of the first battery 10 is divided by the eighth resistor R62 and the ninth resistor R63 and output to the control end of the third MOS transistor Q7. The third MOS transistor Q7 conducts. The second end of the tenth resistor R57 receives the voltage of the standard voltage source (P5V), and the first end of the tenth resistor R57 is grounded through the conducting third MOS transistor Q7. The control end of the fourth MOS transistor Q6 is grounded through the conducting third MOS transistor Q7. Therefore, the third MOS transistor Q7 does not conduct. The output voltage signal of the standard voltage source is output to pin 8 (enable signal terminal) of the charging management chip U5 through the eleventh resistor R608. The charging management chip U5 starts to perform charging and outputs a charging voltage to the second battery 20 (BAT2) through pin 5, and the second battery 20 starts to charge. When the output voltage of the first battery 10 (VBP) is abnormal, that is, when the output voltage of the first battery 10 is less than the fourth preset voltage threshold, the output voltage of the first battery 10 is divided by the eighth resistor R62 and the ninth resistor R63 and output to the control end of the third MOS transistor Q7. The third MOS transistor Q7 does not conduct. The control end of the fourth MOS transistor Q6 obtains the output voltage of the standard voltage source through the tenth resistor R57. At this time, the voltage at the control end of the fourth MOS transistor Q6 is the same as the voltage at the second end of the fourth MOS transistor Q6. Therefore, the fourth MOS transistor Q6 conducts. The standard voltage source is grounded through the eleventh resistor R608 and the conducting fourth MOS transistor Q6. Pin 8 of the charging management chip U5 is grounded through the fourth MOS transistor Q6, and pin 5 of the charging management chip U5 does not output a charging voltage, that is, the second battery 20 is not charged.

[0092] Specifically, the connection relationship between each pin of the charging management chip U5 and related components is as Figure 6 shown. Each pin of the charging management chip U5 and its corresponding functions are: Pin 1 (TEMP) can be used for the battery temperature monitoring function. Figure 6The middle ground setting indicates that this function is not enabled; Pin 2 (PROG) is used to set the charging circuit; Pin 3 (GND) is the power ground; Pin 4 (VCC) is used to connect the power supply; Pin 5 (BAT) is used to connect the positive pole of the battery; Pin 6 (STB) is used for charging completion indication, and corresponding indication signals are output through the CHAGE_STDBY point; Pin 7 (CHG) is used for charging indication, and corresponding indication signals are output through the CHAGE_STATE point; Pin 8 (CE) is the enable signal input terminal (enable signal terminal). R62 and R63 can be voltage-dividing resistors, Q6 and Q7 can be N-channel MOS transistors, R608 and R57 can be pull-up resistors, and R61 can be a charging current setting resistor. C198, C199, C200, and C201 can be filter capacitors. VABT can refer to the network before the fuse of the second battery 20 (BAT). In the existing charge and discharge circuit, it is impossible to achieve anti-reverse charging without adding a diode without changing the circuit structure. However, in this application, anti-reverse charging is achieved through the built-in anti-reverse charging circuit in the above-mentioned charging management chip U5, and no external diode is required.

[0093] In an exemplary embodiment, as Figure 6 shown, the above-mentioned charging circuit further includes a fuse F2, where: the first end of the above-mentioned fuse F2 is connected to the above-mentioned charging management chip U5, and the second end of the above-mentioned fuse F2 is connected to the above-mentioned second battery 20; the above-mentioned charging management chip U5 is further configured to, when the enable signal terminal of the above-mentioned charging management chip U5 receives the above-mentioned charging enable signal, step down the voltage provided by the above-mentioned standard voltage source and output it to the above-mentioned second battery 20 through the above-mentioned fuse F2 to charge the above-mentioned second battery 20. Among them, the fuse F2 can prevent the second battery 20 (BAT2) from being burned out when the charging management chip U5 has an abnormality and causes the charging current to be too large, and plays a protective role for the second battery 20.

[0094] In an exemplary embodiment, the above-mentioned charging circuit further includes a first indicator light and a second indicator light, where: the above-mentioned first indicator light is connected to the above-mentioned charging management chip U5, and the above-mentioned second indicator light is connected to the above-mentioned charging management chip U5; the above-mentioned charging management chip U5 is further configured to light the above-mentioned first indicator light during the charging process of the above-mentioned second battery 20; the above-mentioned charging management chip U5 is further configured to light the above-mentioned second indicator light when the charging of the above-mentioned second battery 20 is completed. As Figure 6As shown, the CHAGE_STATE (charging state) corresponding to the 7th pin of the charging management chip U5 is used to connect to the first indicator light. During the charging process of the second battery 20, the first indicator light is lit to indicate that the second battery 20 is being charged. The CHAGE_STDBY (charging completion state) corresponding to the 6th pin of the charging management chip U5 is used to connect to the second indicator light. When the charging of the second battery 20 is completed, the second indicator light is lit to indicate that the charging of the second battery is completed. Among them, the first indicator light and the second indicator light can be LED lights.

[0095] In an exemplary embodiment, the resistors involved in the above circuit can be encapsulated in the size represented by the 0402 code (i.e., its physical size is 0.04 inches × 0.02 inches (about 1.0 mm × 0.5 mm)), which can miniaturize the above circuit and reduce the volume. In the above circuit, the parameters of the first resistor R610 can be 1M (resistance value Ω), 1% (accuracy), the parameters of the second resistor R621 can be 3.3K, 5%, the parameters of the third resistor R620 can be 3.3K, 5%, the parameters of the fourth resistor R617 can be 500K, 1%, the parameters of the fifth resistor R618 can be 500K, 1%, the parameters of the sixth resistor R619 can be 250K, 1%, the parameters of the seventh resistor R616 can be 1M, 1%, the parameters of the eighth resistor R62 can be 510K, 1%, the parameters of the ninth resistor R63 can be 300K, 1%, the parameters of the tenth resistor R57 can be 5.1K, 1%, the parameters of the eleventh resistor R608 can be 5.1K, 1%. The parameters of the resistor R611 can be 1M, 1%. The parameters of the resistor R61 can be 39.2K, 1%. The parameters of the resistor R21 can be 33K, 1%. The parameters of the resistor R23 can be 715R, 1%. The parameters of the resistor R28 can be 11K, 1%.

[0096] In an exemplary embodiment, the software and hardware in the above circuit can control charging and discharging. When detected by the single-chip microcomputer, it can identify whether the storage battery has lost power to perform lithium battery power continuation to continuously supply power to the vehicle-mounted control system, so that the controller can keep sending information to the data platform; the single-chip microcomputer can also identify whether the storage battery has lost power through the ADC acquisition of the storage battery voltage. If 24V cannot be acquired by ADC and 5V can be acquired, it means that the storage battery has lost power and the 5V power supply after the lithium battery is boosted is already in use.

[0097] The above circuit can be applied to automobiles or similar devices.

[0098] In the description of this specification, the descriptions referring to terms such as "some embodiments", "other embodiments", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0099] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0100] The above-described embodiments only represent several implementation manners of the present application, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation on the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A power-off prevention circuit, characterized in that, It includes a first battery, a second battery, a discharge circuit, and a boost circuit, where: The first battery is connected to the discharge circuit; the rated voltage of the second battery is less than the rated voltage of the first battery; The first battery is used to supply power to the vehicle-mounted control system; The discharge circuit is used to conduct the second battery to the input end of the boost circuit when the output voltage of the first battery is less than the first preset voltage threshold; The boost circuit is used to boost the input voltage at the input end of the boost circuit to the power supply voltage level required by the vehicle-mounted control system to supply power to the vehicle-mounted control system.

2. The power-down prevention circuit according to claim 1, wherein The discharge circuit includes a switch unit, where: The first end of the switch unit is connected to the second battery, the second end of the switch unit is connected to the boost circuit, and the control end of the switch unit is connected to the first battery; The switch unit is used to conduct the first end and the second end of the switch unit when the output voltage of the first battery received at the control end of the switch unit is less than the first preset voltage threshold.

3. The power-off prevention circuit according to claim 2, wherein The switch unit includes a first MOS transistor and a first resistor, where: The first end of the first resistor is grounded, the second end of the first resistor is connected to the control end of the first MOS transistor, the second end of the first resistor is also connected to the first battery, the first end of the first MOS transistor is connected to the second battery, and the second end of the first MOS transistor is connected to the boost circuit; The first MOS transistor is used to conduct the first end and the second end of the first MOS transistor when the control end of the first MOS transistor receives a ground signal through the first resistor, or when the output voltage of the first battery received is less than the first preset voltage threshold.

4. The power-off prevention circuit according to claim 3, wherein The power-off prevention circuit further includes a microcontroller control circuit, where: The microcontroller control circuit is used to output a first voltage to the control end of the first MOS transistor when receiving a low-level signal from the microcontroller; wherein, the first voltage is greater than or equal to the first preset voltage threshold; The first MOS transistor is further used to disconnect the first end and the second end of the first MOS transistor when the control end of the first MOS transistor receives the first voltage.

5. The power-off prevention circuit according to claim 4, wherein, The microcontroller control circuit includes a first triode, a second triode, a second MOS transistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, and the first voltage is the output voltage of the second battery, where: The first end of the second resistor is connected to the single-chip microcomputer, the second end of the second resistor is connected to the first end of the third resistor, the second end of the third resistor is grounded, the first end of the third resistor is also connected to the control end of the first triode, the first end of the first triode is connected to the second end of the third resistor, the second end of the first triode is connected to the first end of the fourth resistor, the second end of the fourth resistor is grounded, the first end of the fourth resistor is also connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the sixth resistor, and the second end of the sixth resistor is connected to the second battery; the control end of the second triode is connected to the second end of the fifth resistor, the first end of the second triode is connected to the second battery, the second end of the second triode is connected to the first end of the seventh resistor, the second end of the seventh resistor is grounded, the first end of the seventh resistor is also connected to the control end of the second MOS transistor, the first end of the second MOS transistor is connected to the second battery, and the second end of the second MOS transistor is connected to the control end of the first MOS transistor; When the vehicle-mounted control system needs to be powered, the single-chip microcomputer inputs a high-level signal to the first end of the second resistor, the first end and the second end of the first triode are turned on, the control end of the second triode receives a voltage signal less than the second preset voltage threshold, the first end and the second end of the second triode are turned on, the control end of the second MOS transistor receives a voltage signal greater than or equal to the third preset voltage threshold, and the first end and the second end of the second MOS transistor are not turned on; When the vehicle-mounted control system does not need to be powered, the single-chip microcomputer inputs a low-level signal to the first end of the second resistor, the first end and the second end of the first triode are not turned on, the control end of the second triode receives a voltage signal greater than the second preset voltage threshold, the first end and the second end of the second triode are not turned on, the control end of the second MOS transistor is grounded through the seventh resistor, the first end and the second end of the second MOS transistor are turned on, the output voltage of the second battery is transmitted to the control end of the first MOS transistor, and the first end and the second end of the first MOS transistor are not turned on.

6. The power-off prevention circuit according to any one of claims 1 to 5, characterized in that The power-off prevention circuit further includes a charging circuit, where: The charging circuit is connected to the standard voltage source, the charging circuit is also connected to the second battery, and the charging circuit is also connected to the first battery; the standard voltage source is obtained by step-down processing of the first battery; The charging circuit is used to step down the standard voltage source and charge the second battery when the voltage of the first battery is greater than or equal to the fourth preset voltage threshold.

7. The power-down prevention circuit according to claim 6, wherein The charging circuit includes a charging management chip and a charging enable circuit, where: The first end of the charging enabling circuit is connected to the first battery, and the second end of the charging enabling circuit is connected to the enabling signal terminal of the charging management chip; the charging management chip is also connected to the standard voltage source; The charging enabling circuit is configured to output a charging enabling signal to the enabling signal terminal of the charging management chip when the voltage of the first battery received at the first end of the charging enabling circuit is greater than or equal to the fourth preset voltage threshold; and is further configured to output a grounding signal to the enabling signal terminal of the charging management chip when the voltage of the first battery received at the first end of the charging enabling circuit is less than the fourth preset voltage threshold; The charging management chip is configured to step down the voltage provided by the standard voltage source and output it to the second battery to charge the second battery when the enabling signal terminal of the charging management chip receives the charging enabling signal.

8. The power-off prevention circuit according to claim 7, wherein The charging enabling circuit includes an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a third MOS transistor, and a fourth MOS transistor, and the charging enabling signal is the output voltage signal of the standard voltage source, wherein: The first end of the eighth resistor is connected to the first battery, the second end of the eighth resistor is connected to the first end of the ninth resistor, and the second end of the ninth resistor is grounded; the control terminal of the third MOS transistor is connected to the second end of the eighth resistor, the first end of the third MOS transistor is grounded, the second end of the third MOS transistor is connected to the first end of the tenth resistor, and the second end of the tenth resistor is connected to the standard voltage source; the control terminal of the fourth MOS transistor is connected to the first end of the tenth resistor, the first end of the fourth MOS transistor is grounded, the second end of the fourth MOS transistor is connected to the first end of the eleventh resistor, the second end of the eleventh resistor is connected to the standard voltage source, and the first end of the eleventh resistor is further connected to the enabling signal terminal of the charging management chip; When the output voltage of the first battery is greater than or equal to the fourth preset voltage threshold, the first end and the second end of the third MOS transistor are turned on, the control terminal of the fourth MOS transistor is grounded through the third MOS transistor, the first end and the second end of the fourth MOS transistor are not turned on, and the standard voltage source outputs the output voltage signal to the enabling signal terminal of the charging management chip through the eleventh resistor; When the output voltage of the first battery is less than the fourth preset voltage threshold, the first end and the second end of the third MOS transistor are not turned on, the standard voltage source outputs a voltage to the control terminal of the fourth MOS transistor through the tenth resistor, the first end and the second end of the fourth MOS transistor are turned on, and the enabling signal terminal of the charging management chip is grounded through the fourth MOS transistor.

9. The power-off prevention circuit according to claim 7, characterized in that, The charging circuit further includes a fuse, wherein: The first end of the fuse is connected to the charging management chip, and the second end of the fuse is connected to the second battery; The charging management chip is further configured to step down the voltage provided by the standard voltage source and output the stepped-down voltage to the second battery through the fuse to charge the second battery when the charging enable signal is received at the enable signal terminal of the charging management chip.

10. The power-off prevention circuit according to claim 7, characterized in that, The charging circuit further includes a first indicator light and a second indicator light, where: The first indicator light is connected to the charging management chip, and the second indicator light is connected to the charging management chip; The charging management chip is further configured to turn on the first indicator light during the charging process of the second battery; The charging management chip is further configured to turn on the second indicator light when the charging of the second battery is completed.

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